Variable displacement pump



p 7 s. HAWXHURST 2,807,215

VARIABLE DISPLACEMENT PUMP Filed July 28, 1955 2 Sheets-Sheet 1 Inventorstgphen Hawxhm'st E: d-1 m QQWM 2,807,215 Patented Sept. 24, 1957 UnitedStates Patent OfiFice The present invention relates to variabledisplacement pumps which are employed for feeding or delivering fluidsin predetermined quantities. More particularly, the invention isconcerned with a variable displacement pump of this character in whichthe pumping action is obtained by the transmission of applied pumpingforce through a confined or partially confined liquid mass interposedbetween a solid piston and a floating member, the latter,

displacing the fluid and thereby subjecting it to the pumping action.

In carrying out the principles of the present invention, briefly, theinvention contemplates the provision of a liquid filled cylinder inwhich there is disposed a reciprocable driving piston or plunger thestroke of which remains substantially constant, which is to say that thefrequency and amplitude of its reciprocation does not vary. Alsodisposed within the cylinder and reciprocable therein is a freelyfloating piston and interposed between the two pistons is a column of anincompressible fluid, i. e. a liquid, the column being bodilydisplaceable in either direction within the cylinder under the influenceof the movements of the first piston and the liquid column actingdirectly upon the floating piston to reciprocate the latter in timedrelation to the reciprocation of the driving piston. The displacementsof the floating piston may be employed for effecting displacements ofthe fluid undergoing pumping, either directly by forcing portions of thefluid out of the cylinder and replacing the same with each completestroke of the floating piston, or the displacements of the floatingpiston may be transmitted to a displaceable flexible barrier which maybe in the form of a movable diaphragm through a second liquidcolumn'interposed between the floating piston and diaphragm, theflexible barrier serving to seal the fluid undergoing pumping from entryinto the cylinder. In the former instance the floating pistonconstitutes the actual pumping element of the system while in the latterinstance the flexible barrier constitutes the pumping element.

Variation in the displacements of the fluid undergoing pumping, ineither instance outlined above, is effected by regulably bleeding aportion of the liquid column existing between the driving piston and thefloating piston so that upon each pressure stroke of the driving pistonagainst the liquid column a predetermined portion of the column mayescape from the cylinder while that portion Which remains within thecylinder will become effective to displace the floating piston. Thus theactual displacement of the floating piston during each pressure strokeof the driving piston will be a function of the rate of bleeding of theliquid from the column thereof, maximum displacement taking place whenno bleeding is permitted and minimum displacement taking place whenmaximum bleeding is effected.

Fluid pumps constructed in accordance with the principles of the presentinvention have a wide variety of applications, one important applicationbeing in connection with the pumping of corrosive fluids or fluids whichare diflicult to seal in that they attack the usual pump packing orsealing elements ordinarily associated with conventional pumpingapparatus. Another and similar application of the present pumpingapparatus is in connection with the pumping of fluids which arepotentially hazardous in that they react explosively in the presence ofbituminous or other lubricating oils ordinarily em- 2 ployed withconventional pumping devices. Numerous other uses for the presentpumping apparatus are contemplated and, in general, the same will befound useful for the pumping of fluids, whatever be their nature, ininstallations where it is desired that the fluid shall remainuncontaminated by contact with other fluids and, toward I this end, theinvention provides for complete or absolute isolation of the fluidundergoing pumping from lubricating oils, pressure liquids such as maybe employed in the liquid motivating column of thepumping system asoutlined above, condensation liquids or the like, or from foreignliquids or abrasive particles and other foreign matter whatever maybe'its source. p

The provision of a variable displacement pump of the character brieflyoutlined'above being among the principal objects of the presentinvention, a further object is to provide such a pump in which theliquid bled from the motivating column of pressure liquid isautomatically replaced during each stroke of the driving piston so thatthe volume of the liquid column will not become permanently diminishedand will at the commencement of each stroke of the driving piston remainconstant.

Astill further object of the invention is to provide a pumping apparatusof this character in which the pumping and sealing diaphragm employedfor the displacement of the fluid undergoing pumping is of an extremelyflexible nature and is therefore capable of a large degree ofdistortion, thus enabling large displacements of fluid during eachstroke of the driving piston, particularly when the apparatus isadjusted for maximum pumping effect.

Yet another object is to provide a variable displacement pump utilizinga driving piston and a diaphragm pumping element in conjunction with abody' of hydraulic fluid between the piston and diaphragm, in which thediaphragm is so constructed that it is not subject to as much strain asthe usual diaphragm employed in diaphragm pump constructions and whichtherefore will not require frequent, if any, repair or replacementduring the life of the pump; i i

Another object of the invention is to provide a variable displacementpump of the character briefly outlined above which will handle corrosiveor valuable fluids without loss of such fluids by leakage through anypart of the pump system.

The provision of a variable displacement pump which is extremely simplein its construction; one which is comprised of a minimum number ofmoving working parts and which therefore is unlikely to get out oforder; one which is capable of ease of assembly and disassembly forpurposes'of inspection of parts, replacement or repair; one which isrugged and durable and which therefore is possessed of a comparativelylong life, one which is capable of asmooth and silent operation; onewhich is capable of being regulated for difierent fluid displacementswithout necessitating shutting down of the pump by a simple and singlemanual adjustment, and one which otherwise is well adapted to performthe services required of it are further desirable features that havebeen borne in mind in the production and development of the presentinvention.

Numerous other objects and advantages of the invention, not at this timeenumerated, will become'more readily apparent as the nature oftheinvention is better understood.

In the accompanying two sheets of drawings forming a part of thisspecification one illustrative embodiment of the invention has beenshown by way of example.

In these drawings:

Fig.- 1 is a fragmentary sectional view, somewhat schematic in itsrepresentation, taken substantially longitudinally and centrally througha pump assembly embodying the principles of the present invention.

Fig. 2 is a sectional view similar to Fig. 1 showing the pump parts inpositions which are displaced from the positions in which they are shownin Fig. 1, and

Figs. 3, 4 and 5 are diagrammatic views illustrating the manner in whichvariations in linear displacement of the effective pump parts serve toeffect variations in the volumetric displacement of the fluid undergoingpumping.

Referring now to the drawings in detail and in par ticular to Figs. 1and 2, the pump construction of the present invention involves in itsgeneral organization a cylindrical pump casing in which there isslidably disposed a piston 12 capable of being driven in itsreciprocating movements by any prime mover, as for example through themedium of a crank pin 14 and connecting rod 16 such as has beendiagrammatically shown in Figs. 3, 4 and 5 A second stemless or floatingpiston 18 is also slidably disposed within the casing 10 in spacedrelation with respect to the piston 12 and a column 20 of anincompressible liquid is interposed between the pistons 12 and 18 sothat the reciprocating movements of the piston 12 may be imparted to thefloating piston 18 through the column 20, alternate compression andsuction strokes of the piston 12 serving to move the piston 18 to theright and left respectively as viewed in The pistons 12 and 18 aregrooved circumferentially to receive suitable packing material 22 whichmay be in the form of conventional 0 rings which are sufliciently tightas to prevent egress of the liquid from the column around the respectivecylinders. prising the column 20 may be composed of any suitable fluidas for example a hydrocarbon oil or the like.

The path of movement of the floating piston 18 within the casing 10 islimited by a pair of spaced abutments 24 and 26 which may be in the formof split rings receivable in internal annular grooves 28 formed in thecylinder wall. The piston 18 is movable between the two abutments 24 and26 from a fully retracted position wherein it engages the abutment 24 toa fully advanced position wherein it engages the abutment 26. Theabutments are spaced apart longitudinally of the cylinder 10 a distancewhich is substantially equal to the amplitude of the stroke of thepiston 12 plus the longitudinal thickness of the piston 18 so that whenthe column 20 is effectively sealed from escape from the casing 10 thefull stroke of the piston 12 will be effective to move the piston 18 andthe reciprocal movements of the two pistons will be equal in amplitude.

The liquid mass which comprises the column 20 is supplcd to the casing10 between the two pistons 12 and I 18 through an inlet 30 communicatingwith a conduit 32 leading from a suitable sump, reservoir or constanthead pump (not shown) and in which conduit there is interposed a one-wayvalve 34 of conventional design. The valve 32 is so designed that theinlet 30 is at all times effectively closed during the entirecompression stroke of the piston 12, and is also closed during thatportion of the suction stroke of the piston 12 wherein the piston 18 iscapable of free travel between the abutments 24 and 26. Thus, with theliquid column 20 sealed oif from escape from the casing 10, the valve 34will remain closed and no fluid will be drawn into the column 20 fromthe sump except possibly a negligible amount of replacement liquid thatmay be pulled through the valve 34 after a long period of operation withan attendant slight loss of the liquid.

The valve 34 is in the form of a casing 36 having a valve seat 38associated therewith and normally closed by a valve element in the formof a ball 40 which is spring pressed as at 42 against the seat in theusual manner of operation of such one-way devices. The spring 42 is sodesigned that it will maintain the ball 40 seated at pressures withinthe column 20 which are somewhat below the pressure maintained withinthe sump which usually is atmospheric pressure. By such an ar- Theliquid mass com- 9 Cir rangement the suction stroke of the piston 10will be effective through the column 20 to move the piston 18 to itsretracted position despite any reduction of internal pressure developedwithin the column 20 due to the frictional drag of the floating piston18.

As will be described subsequently, means are provided for varying theamplitude of the effective stroke of the floating piston 18 toconsequently vary the volumetric displacement of the fluid undergoingpumping. It is deemed suflicient at present to state that this means isin the form of a bleeder conduit 44 which communicates through thecasing 10 with the liquid column 2% and in which there is interposed avariable orifice bleeder valve designated in its entirety at 46.

The above description has been based upon the more or less diagrammaticillustration of the invention shown in Figs. 1 and 2 wherein the drivingpiston or plunger 12. and the stemless or floating piston 13 areillustrated as being reciprocable in a common cylindrical casing 10. Theabutment 24, in effect, divides the cylindrical casing 19 into twooperating cylinders designated at 41 and 43 respectively, the piston 12.operating in the cylinder 41 and the piston 18 operating in the cylinder43. The incompressible liquid column 21 which is interposed between thetwo cylinders 12 and 18 is bodily shiftable with the pressure andsuction strokes of the piston 12 so that portions thereof aretransferred from one cylinder to the other to translate the movements ofthe piston 12 into corresponding movements of the piston 18. It shouldalso be noted at this point that when the floating piston 18 is drawnrearwardly against the abutment 24 during the suction stroke of thepiston 12, the cylinder 43 is sealed from the cylinder 41 during theremainder of any suction stroke which the piston 12 may make after suchengagement between the floating piston 18 and the abutment 24 so that alost motion between the two pistons will exist during which time thevalve 34 will admit replacement fluid to the liquid column 20. It willbe understood of course that when the variable orifice or bleeder valve46 is closed, no liquid from the column 2% may escape and therefore thevalve 34 will remain inactive in the absence of replacement fluidrequirements.

Still referring to Figs. 1 and 2, the end of the cylinder 10 remote fromthe driving piston 12 communicates with a pump chamber 58, the casing 52of which is provided with an end wall 53 having a fluid inlet port 54and a fluid outlet port 56 formed therein. The inlet port 54communicates through a conduit 58 with the body of fluid undergoingpumping while the outlet port 56 is connected to the discharge conduit6%). Suitable oneway valves 62 and 64 are interposed in the conduits 62and s4 respectively.

interposed between the otherwise communicating cylinder 1t? and casing52 is a deformable flexible barrier 66 which may take the form of adiaphragm, preferably one of deep cup-shape bellows-like configurationhaving one end closed as at 68 and the other end open as at 7t? andprovided with a series of bellows folds 71 and a laterally extendingannular flange 72. The flange 72 is interposed between cooperatingflanges 74 and 76 provided on the cylinder 11) and casing 52respectively and is sealingly clamped therebetween by means of a seriesof clamping bolt assemblies 73. Disposed partly within the cylinder 10and partly within the pump chamber casing 52 is a second column 79 of anincompressible liquid, this latter column being interposed between thefloating piston 18 and the diaphragm 56. The cylinder 10 may have formedtherein an injection opening or port 80 normally closed by a threadedfiller plug 82 and by means of which the space existing between thepiston 18 and diaphragm 66 may be filled with the liquid of the column79.

The particular liquid which cooperates to make up the incompressiblecolumn 79 will be chosen according to engineering exigencies toaccommodate the particular installation with which the pump isassociated. Where ordinary non-corrosive and chemically stable fluidsare undergoing pumping, the column 79 may be composed of a suitablehydrocarbon oil. However, where the fluid being pumped is of a corrosivenature, or is such that it will react explosively or otherwise with suchoil, then it is desirable to select for the column 79 an inert liquidwhich will present no hazard in the event of rupture of the diaphragmand consequent passage of the pumpage therethrough. For example, wherethe liquid undergoing pumping is liquid fiourine which reactsexplosively inthe presence of ordinary hydrocarbon oils, the column 79may becomprised of an inert fluid such as a liquid 'flourinatedhydrocarbon.

The material employed in the construction of the diaphragm 66 as well asthe specific shape thereof Will be chosen appropriately for the servicerequired of it. For ordinary installations the diaphragm 66 may beconstructed of an elastomeric material such as rubber or a rubbersubstitute having a high degree of resilience and. a high coeflicient ofelasticity, in which case the diaphragm need not be of deep cup-shapeconfiguration.

and the bellows folds'71 may be dispensed with. Under certain conditionsthe diaphragm 66 may be in the form of a deformable disk-like membranethe peripheral edges of which are clamped between the flanges 74 and 76of the casing 52 and cylinder respectively. For corrosive chemicalinstallations the diaphragm 66 is preferably made of apolytetrafluoroethylene polymer which is manufactured as described inIndustrial and Engineering Chemistry, volume 318, page 870 of theSeptember, 1946 issue, and is sold by E. I. du Pont de Nemours & Co.under the trade name Teflon. This material is characterized by itschemical inertness which is characteristic from extremely lowtemperatures up to 572 F. Through thi wide temperature range it resiststhe attack of corrosive reagents and dissolution by solvents. Thediaphragm may be machined from molded Teflon to have a closed end andmay assume any of the forms shown and described in the patent to FrankE. Payne et al., Number 2,758,856. Molded Teflon is a tough waxy solid,White to grey in color and it may be held at elevated temperatures overlong periods of time.

From the above description it will be seen that Teflon is ideally suitedas the diaphragm material for installations involving the pumping ofeither hot or cold corrosive fluids. Although Teflon has satisfactorytensile strength it lacks the resilience ordinarily required in theusual disk-shape or shallow cup diaphragms so that when it is employedfor the diaphragm in the present pump construction it is desirable toresort to a deep cup construction with the cup sides having the seriesof bellows folds 71 to permit the required linear elongation of thediaphragm with a consequent large displacement of fluid from the pumpchamber 50 at each pressure stroke of the driving piston 12. As shown inFigs. 1 and 2, the diaphragm is movable under the impelling influence ofthe liquid column 79 from a retracted or collapsed position wherein theend wall 68 thereof is remote from the end wall 53 of the pump casing 52to an extended or expanded position wherein said end wall 68 is in closeproximity to the end wall of the casing. It is obvious that theelongation of the diaphragm 66 will serve to expel a quantity of theliquid undergoing pumping from the pump chamber 50 through the one-wayvalve 64 and that contraction of the diaphragm will draw a replacementfor it through the pump chamber 50 through the one-way valve 62 so thatupon repeated successive expansional and contractional movements of thediaphragm an intermittent passage of the pumpage from the source of thefluid to a point of discharge will take place in the normal manner ofreciprocal type pumps.

As previously stated, the volumetric displacement of fluid undergoingpumping may be varied by regulably wa t p controlling the bleeding ofliquid in the column 2.0 through the conduit 44 and bleeder valve 46.'The valve 46 is of conventional design and includes the usual valvecasing 100 which is interposed in the conduit and which is provided witha liquid inlet port 102 and a liquid outlet port 104 both of which portscommunicate with a valve chamber'106. The valve chamber 106 is providedwith a conical valve seat 108 designed for cooperation with a conicalvalve element 110 formed at the free end of a valve stem 112. The valvestem 112 is formed with an enlarged threaded portion 114 threadedlyreceived in the central bore 116 of a tubular guide cylinder 118 throughwhich the valve stem 112 projects. The guide cylinder 118 is formed withthe usual valve packing assembly 120 and a hand wheel 122 carried at theouter end of the valve stem 112 facilitates manipulation of the latter.

From the above description it will be seen that when the bleedervalve'116 is fully closed so that flowof the liquid of the column 20through the bleeder conduit 44 is prevented, the full stroke of thedriving piston 12 will be effective through the liquid column 20 toeffect a full stroke of the floating piston 18 so that this latterpiston will move from its retracted position in contact with theabutment 24 to its fully advanced position in contact with the abutment26. Such full stroke of the floating piston 18 will similarly beeffective through the liquid column 79 upon the diaphragm 66 and thelatter will become expanded to the fullest extent of which it is capableand, under such conditions, maximum displacement of fluid from the pumpchamber 50 will take place. This maximum displacement by the pumpconstruction with the valve 46 fully closed its diagrammaticallyillustrated in Fig. 3. It is to be noted in connection with thisdiagrammatic illustration that a disk-type resilient diaphragm capableof linear expansion has been shown in lieu of the bellows type diaphragmof Figs. 1 and 2. It will be appreciated however that irrespective ofthe particular form of diaphragm employed, the essential features of theinvention are at all times preserved. In the illustration of Fig. 3 theposition of maximum displacement of the pistons 12 and 18 and of thediaphragm 66 have been illustrated in full lines and the comparativelylarge illustrated displacement of the diaphragm 66 represents a maximumdisplacement of fluid from the pump chamber 50.

In Fig. 4 the bleeder valve 46 is shown in a partially open positionwherein a predetermined rate of escape of the fluid of the column 20through the bleeder conduit 44 to the sump (not shown) is permitted.Under such conditions the constant head of the fluid undergoing pumpingin the pump chamber 50 will reactthrough the floating piston '18 tobuild up a back pressure in the liquid column 20 so that a portion ofthe fluid in this column will be forceably expelled through the bleederconduit 44 and valve 46, while the liquid of the column 20 which is notexpelled due to the restriction of the size of the valve opening leadingfrom the chamber 106 will become effective on the floating piston 18 tomove the same forwardly in the cylinder 10 toward its fully advancedposition. However, in this instance, the quantity of liquid in'thecolumn 20 being diminished by the escape of a portion of the fluidthrough the valve 46, will drive the floating piston only a portion ofits normal full stroke so that when the driving piston 12 has movedthrough its full stroke, the floating piston 18 will have moved to somepoint represented by its dotted line position in Fig. 4. Such partialstroke of the floating piston 18 will cause a correspondingly smallerdisplacement of the liquid contained in the column 79 so that onlypartial expansion of the diaphragm '66 will take place. This partialexpansion of the diaphragm 66 will result in the displacement of acorrespondingly smaller quantity of the fluid or pumpage containedwithin the pump chamber 50.. It is obvious that the degree of-opening ofthe valve 46 will control the rate of displacement of the fluid from thepump chamber 50, the greater the valve opening, the lesser thedisplacement of such fluid and vice versa.

'In Fig.5 anextreme condition has been illustrated wherein the bleedervalve 46 is moved to its fully open position so that the fluid containedwithin the column 20 may pass more or less freely through the conduit 44and valve 46 to the sump during the advance stroke of the driving piston12. With the liquid in the pump chamber 50 maintained at its constanthead, the forward stroke of the piston 12 will serve to drive all of theliquid contained within the column 21 except for a small residual amountthereof into the bleeder conduit 44 while the floating piston 18 willnot move from its position in engagement with the abutment 24. Thus, asshown in Fig. 3, there will be no displacement of the diaphragm 66 andas a consequence no pumping action will take place in the pump chamber50.

Inasmuch as the disclosure of the drawings is schematic in itsrepresentation, the invention is obviously not to be limited to thisrepresentation which is only illustrative of the principles involved.For example, while the pistons 12 and 18 are shown as being reciprocablein a common cylinder, these pistons may be operatively disposed inseparate and independent but communicating cylinders and for purposes ofclaiming herein the separate parts of the cylindrical casing 10 in whichthe two pistons reciprocate may be regarded as being independentcylinders which are in communication with each other. Likewise, whilethe diaphragm 66 has been interposed between the fluid in the pumpchamber 50 and the inert liquid of the liquid column 7 9, thisarrangement being advisable where corrosive or otherwise hazardouspumpage is concerned, the diaphragm 66 may, if desired, be omittedaltogether and the floating piston 18 permitted to operate directly uponthe pumpage. Additionally, while the displacea'ble member 66 forpurposes of illustration has been shown in the form of a bellows-typediaphragm in Figs. 1 and 2 and has been shown as a disk-type diaphragmin Figs. 3, 4 and 5, this displaceable member may, if desired, assumethe form of a second floating piston similar to the piston 13 andoperable in a cylinder the walls of which define the pump chamber 50.The invention therefore is not to be limited to the disclosure herein asthese and other changes may be resorted to without departing from thespirit of the invention. Only insofar as the invention has particularlybeen pointed out in the accompanying claims is the same so limited.

What I claim is:

1. In a device for pumping fluids, a pump housing defining a chamberprovided with valved inlet and outlet conduits, a cylinder connected tosaid housing adjacent said chamber, a driving plunger mounted forreciprocation said cylinder, a free piston in said cylinder between thechamber and plunger, 21 displaceable barrier interposed between saidpiston and pump chamber and operable upon displacement in one directionto force fluid from the pump chamber through said outlet conduit andupon displacement in the opposite direction to draw fluid into said pumpchamber through said inlet conduit, an incompressible column ofactuating liquid effectively interposed between said piston and barrierfor translating the movements of said piston in opposite directions intodisplacements of said barrier, a second column of liquid interposedbetween the piston and plunger, an inlet port in communication with saidsecond liquid column, a one-way valve in communication with said portand operative to admit liquid to said port when a predetermined minimumdegree of pressure exists within said second column, a bleeder port incommunication with said second liquid column, and a variable orificevalve in communication with said bleeder port.

2. In a device for pumping fluids, a pump chamber having a wall providedwith valved inlet and outlet conduits, a first cylinder in communicationwith said chamber, a floating piston slidably disposed in said floatingpiston and diaphragm, a second cylinder in fluid communication with thefirst cylinder, a driving plunger ,mounted for reciprocation in saidsecond cylinder, means connected to the plunger for reciprocating saidplunger, a second incompressible column of actuating liquid interposedbetween said driving plunger and said floating piston, an abutment insaid first cylinder and extending intothe path of movement of thefloating piston for limiting the movement thereof in said cylinderduring the suction stroke of said plunger, said abutment in combinationwith the floating piston serving to seal said first cylinder from thesecond cylinder when the floating piston is in contact with saidabutment, an inlet port in communication with said second liquid column,a one-Way valve in communication with said inlet port and operable toadmit liquid to said port when a predetermined minimum degree ofinternal pressure exists within said second column, a bleeder port incommunication with said second liquid column and a variable orificevalve in communication with said bleeder port.

3. In a device for pumping corrosive fluids, the combination set forthin claim 2 wherein said first liquid column is comprised of liquid whichis chemically .inert with respect to the corrosive fluid undergoingpumping and in which said flexible diaphragm is comprised of apolytetrafluoroethylene polymer.

4. In a device for pumping fluids, a pump casing having one open end, afluid inlet and a fluid outlet for said casing, an inlet valve and anoutlet valve in communication with said fluid inlet and fluid outletrespectively, an elongated cylinder casing having a cylindrical boreextending therethrough in communication at one end with the interior ofsaid pump casing, a flexible diaphragm extending across one end of saidcylindrical bore and serving to seal the interior of said pump casingfrom the interior of said cylindrical bore, a floating pistonreciprocable in said bore, a first incompressible column of liquidinterposed between said floating piston and said diaphragm, a drivingpiston mounted for reciprocation in said bore on the side of saidfloating piston remote from said pump casing, a second incompressiblecolumn of liquid interposed between said driving piston and saidfloating piston, an abutment disposed within said cylindrical casing onthe side of said floating piston remote from said pump chamber andagainst which said floating piston is adapted to bear to limit themovement of the latter in one direction during the suction stroke ofsaid driving piston, an inlet port in communication with said secondliquid column,

a one-way valve in communication with said second port and operable toadmit liquid to said port when a predetermined minimum degree ofinternal pressure exists within said second column, a bleeder port incommunication with said second liquid column and a variable orificevalve in communication with said bleeder port.

References Cited in the file of this patent UNITED STATES PATENTS1,301,485 Mueller Apr. 22, 1919 1,650,377 Nixon Nov. 22, 1927 1,696,825White Dec. 25, 1928 2,041,468 Grubbs May 19, 1936 2,424,595 Warren July29, 1947 2,496,711 Goddard Feb. 7, 1950 FOREIGN PATENTS 350,817 GreatBritain June 18, 1931 637,589 Great Britain May 24, 1950 t 673,850France Oct. 14, 1929

